DRIVE AND MOTIVATION 



l 5°3 



reduces or removes the peripheral local stimulation. 

 While the behaviorists decried any reference to 

 subjective experience, it seems unlikely that this 

 theory was hurt by the fact that it implied the removal 

 of 'unpleasant' peripheral stimulation with consequent 

 'relief or 'pleasure.' 



Despite the general acceptance of Cannon's local 

 theories and their extension and oversimplification 

 by others, in time many cogent arguments against 

 this viewpoint developed. In the first place, human 

 cases were found where sensations of hunger and 

 thirst existed apart from local stimulation. Some 

 people never seemed to experience gastric contrac- 

 tions, yet they ate; people with congenital absence of 

 salivary glands distinguished between their chroni- 

 cally dry mouths and thirst and were able to drink 

 appropriately to their water deficits (150). Further- 

 more, it was shown that denervation or surgical 

 excision of the stomach did not destroy hunger in 

 man (74, 163) or the regulation of food intake in 

 animals (159) or the animal's ability to work and 

 learn for food rewards (11, 1 08). 



Finally, as further investigations were made into 

 the physiological basis of hunger, thirst, sexual be- 

 havior, etc., it became apparent that local stimula- 

 tion could only be one of several factors contributing 

 to these kinds of motivated behavior. By no means 

 can gastric contractions or local throat dryness, etc. 

 be considered essential in the arousal, maintenance 

 and satiation of such motivated behavior. On the 

 other hand, we have no evidence at present enabling 

 us to deny that local factors make some contribution 

 or even to argue against the possibility that they 

 might provide a most important basis of the sensa- 

 tions accompanying motivation; or that an extremely 

 important part of the motivation of animals working 

 and learning for rewards might not be the reduction 

 or removal of peripheral stimulation. These are 

 matters to be assessed experimentally, and we will 

 discuss some of the relevant studies later. 



HOMEOSTASIS AND SELF-REGULATORY BEHAVIOR 



The second important physiological advance in 

 the study of motivated behavior was made in the 

 bold conceptualizations and extensive investigations 

 of Richter (129, 130). A behaviorist with an organ- 

 ismic point of view, he saw that motivated behavior 

 could be of adaptive value in the survival of the 

 organism because of its essential contribution to the 

 maintenance of the internal environment. Starting 



with the conceptualizations of Claude Bernard and 

 with Cannon's homeostasis, Richter conceived of 

 motivated behavior as self-regulatory behavior in the 

 sense that it may correct deviations of the internal 

 environment in cooperation with the more automatic 

 physiological mechanisms. For example, the warm- 

 blooded animal can regulate its temperature by 

 dietary selection, nest building or simply moving 

 from a hot to a cooler environment or vice versa, as 

 well as by shivering, piloerection, panting, sweating, 

 and vasomotor and metabolic changes. Quite clearly 

 such behavioral responses as these have all the 

 characteristics of motivated behavior, and their 

 investigation has given valuable insight into the physi- 

 ology of motivation. 



In his extensive investigations, Richter was able 

 to show that the organism actually is sensitive to 

 main of its own physiological needs and will develop 

 motivated behavior appropriate to the correction of 

 those needs and the maintenance of the internal 

 environment. For example, he showed that rats were 

 able to select their own diets, cafeteria-style, from a 

 complete array of dietary components (129). Further- 

 more, shifts in amounts of different substances ingested 

 followed in accordance with prior dietary restrictions, 

 changes in environmental temperature, endocrine 

 gland extirpations, pregnancy, etc. For example, the 

 parathyroidectomized rat ingests abnormally large 

 amounts of calcium and abnormally small amounts 

 of phosphorus, quite in keeping with its physiological 

 mills (127). Similarly, the adrenalectomized rat 

 keeps up its sodium level by ingesting excessive 

 amounts of sodium chloride solutions (126), and so 

 on through main strikini; examples. 



As a behaviorist, Richter saw no advantage in 

 invoking instinct to account for this remarkable 

 behavior. Instead, he sought an explanation in terms 

 dI some local expression of the state of physiological 

 need, after the fashion of Cannon's theories, in 

 chansjes in peripher.il receptor mechanisms. Thus, he 

 attributed the strong salt hunger of the adrenalecto- 

 mized rat to an increase in sensitivity of the salt 

 receptors in the mouth, for the adrenalectomized rat 

 shows a preference for concentrations of sodium 

 chloride solutions so weak that the normal rat fails to 

 select them over water (10, 128). The fact that, 

 following taste-nerve section, adrenalectomized rats 

 failed to select salt and died (129) was taken to 

 support the role of the peripheral receptor change in 

 this motivation, but the delect may have been in the 

 capacity to detect salt rather than in the motivation. 

 As a matter of fact, electrical recording from the 



